This invention relates to a method for joining components in titanium aluminide by brazing.
Components in titanium aluminide (TiAl) are primarily known in the aeronautical sector. For example, turbine blades, bearings, casing parts and similar items are made of these materials.
A joining method for such components is shown in U.S. Pat. No. 5,318,214, for example. In this method, the TiAl components are joined by means of a braze which, together with the components, is heated in a furnace. This joining method is disadvantageous in that the requirement for a furnace (for example a vacuum furnace or a protective gas furnace) entails high equipment investment as the components are to be appropriately positioned relative to and pressed against each other. Such a method, therefore, does not make good commercial sense. A further disadvantage is the thermal impact on the components which may result in undesirable structural changes. Also, undesired distortion may occur, in particular when joining thin-gage sheets.
U.S. Pat. No. 5,785,775 shows an electric welding method for components made of titanium aluminides. This method may, however, cause cracking flaws in welds which must be removed in further, expensive processing operations (see U.S. Pat. No. 5,873,703 A).
A laser welding method for components in titanium aluminide using protective gas is described in Specification U.S. Pat. No. 4,990,741 A. This method also incurs high investment, and affects the structure of the components, as the components must be heated sufficiently to become molten at the weld joint for the welding process.
Summarizing, then, no commercially sensible method for the joining of components, in particular of titanium aluminide sheet, is currently available.
Furthermore, all known methods have the disadvantage that geometrically complex components, in particular sheet-metal structure parts, must be kept in position during the joining process while applying continuous pressure and maintaining stringent tolerances. The different heat expansion of the components to be joined, and of the holding and pressure-application devices used during the heating and the actual joining process, involves high equipment investment. This results in quite considerable manufacturing costs.